Introduction:
SWIM decided to investigate an alternate method of producing isopropanolic hydrogen chloride that doesn't involve the usual gassing method.
The gassing method is seriously nasty to work with. Hydrogen chloride fumes are no joke.
SWIM believes this is a safer and more convenient method of preparing this very useful reagent.
Another benefit is that it can be stored for longer periods of time without degradation, that way, you can use it when you need it
to crystallize a certain amine as the hydrochloride salt without the need for polar aprotic solvents like acetone or diethyl ether.
At the present moment it is unclear what the molarity of the solution is, a titration was not performed.
It is also unclear how much water may have made its way into the iPrOH, however it is believed to be nearly anhydrous.
Required Equipment:
- A large mason jar.
- 2 smaller containers that are able to fit inside the larger mason jar.
A salt/pepper shaker worked nicely since they tend to be tall and narrow.
Required Reagents:
- Concentrated sulphuric acid (drain cleaner will work) 93-98%
- Concentrated muriatic acid/hydrochloric acid approx 31%
- Anhydrous magnesium sulphate
- 99% isopropanol
Instructions:
1. Take the large mason jar and fill the bottom of the jar with a healthy portion of concentrated sulphuric acid.
2. Next take one of the small salt/pepper shakers and fill the bottom with a reasonable portion of anhydrous magnesium sulphate.
3. Once this is done, pour isopropanol into the shaker you just filled with anhydrous magnesium sulphate.
4. Very carefully drop the isopropanol container into the large mason jar making sure not to spill anything.
5. Finally take the remaining shaker and also drop it into the mason jar. DO NOT fill it with hydrochloric acid beforehand.
It must be empty. If you spill any acid as you place it inside you will have all sorts of fun problems to worry about!!! Just run at that point.
6. Using a pipette you can now slowly and very carefully fill up the empty shaker with hydrochloric acid.
7. To prevent the mason jar from detonating, spraying liquid/gaseous acid and shards of glass everywhere you must ensure that the lid
is on loosely so that any over pressure has a chance to vent outwards. That said the lid is necessary to allow the system to reach equilibrium.
8. Now just leave it in a well ventilated area and walk away for a few days/1 week.
You can check on it occasionally to make sure that nothing funky is happening. Make sure to check the lid!!!
The completed set up should look something like this:
Why/how does this process work?
- Aqueous hydrogen chloride has a slight vapor pressure, meaning it will very slowly enter the gas phase.
- The concentrated sulphuric acid at the bottom of the container serves to dehydrate the gaseous hydrogen chloride by stripping it of any water.
- Over time an atmosphere of dry hydrogen chloride will begin to accumulate in the container.
- As this occurs HCl gas will slowly start to migrate over into the isopropanol container and enter into solution.
- The anhydrous magnesium sulphate serves to remove the remaining 1% of water in the isopropanol as well as any that might come over during the reaction.
Possible improvement that was not attempted:
If you consider that the enthalpy change of protonation is -ve (in other words exothermic) you can shift the reaction equilibrium towards product formation via Le Chatelier's principle.
This can be done by removing heat from the system. Placing the jar in the fridge might help increase the solubility of HCl in the isopropanol although I can't say for certain what will happen.
The original gassing method was also conducted using cold conditions, this is why I mention it.
Proof that this actually works:
A small amount of sodium bicarbonate (baking soda) was placed into a beaker followed by the isopropanol that was now acidic,
after which carbon dioxide was released indicating the presence of dissolved hydrogen chloride.
I didn't fake this, the bicarbonate clearly doesn't dissolve like it would in water.
The effervescence is also extremely slow because the reaction is heterogeneous and not homogeneous like it would be with water present.
Thank you for reading and I hope you found this informative. Cheers!
SWIM decided to investigate an alternate method of producing isopropanolic hydrogen chloride that doesn't involve the usual gassing method.
The gassing method is seriously nasty to work with. Hydrogen chloride fumes are no joke.
SWIM believes this is a safer and more convenient method of preparing this very useful reagent.
Another benefit is that it can be stored for longer periods of time without degradation, that way, you can use it when you need it
to crystallize a certain amine as the hydrochloride salt without the need for polar aprotic solvents like acetone or diethyl ether.
At the present moment it is unclear what the molarity of the solution is, a titration was not performed.
It is also unclear how much water may have made its way into the iPrOH, however it is believed to be nearly anhydrous.
Required Equipment:
- A large mason jar.
- 2 smaller containers that are able to fit inside the larger mason jar.
A salt/pepper shaker worked nicely since they tend to be tall and narrow.
Required Reagents:
- Concentrated sulphuric acid (drain cleaner will work) 93-98%
- Concentrated muriatic acid/hydrochloric acid approx 31%
- Anhydrous magnesium sulphate
- 99% isopropanol
Instructions:
1. Take the large mason jar and fill the bottom of the jar with a healthy portion of concentrated sulphuric acid.
2. Next take one of the small salt/pepper shakers and fill the bottom with a reasonable portion of anhydrous magnesium sulphate.
3. Once this is done, pour isopropanol into the shaker you just filled with anhydrous magnesium sulphate.
4. Very carefully drop the isopropanol container into the large mason jar making sure not to spill anything.
5. Finally take the remaining shaker and also drop it into the mason jar. DO NOT fill it with hydrochloric acid beforehand.
It must be empty. If you spill any acid as you place it inside you will have all sorts of fun problems to worry about!!! Just run at that point.
6. Using a pipette you can now slowly and very carefully fill up the empty shaker with hydrochloric acid.
7. To prevent the mason jar from detonating, spraying liquid/gaseous acid and shards of glass everywhere you must ensure that the lid
is on loosely so that any over pressure has a chance to vent outwards. That said the lid is necessary to allow the system to reach equilibrium.
8. Now just leave it in a well ventilated area and walk away for a few days/1 week.
You can check on it occasionally to make sure that nothing funky is happening. Make sure to check the lid!!!
The completed set up should look something like this:
Why/how does this process work?
- Aqueous hydrogen chloride has a slight vapor pressure, meaning it will very slowly enter the gas phase.
- The concentrated sulphuric acid at the bottom of the container serves to dehydrate the gaseous hydrogen chloride by stripping it of any water.
- Over time an atmosphere of dry hydrogen chloride will begin to accumulate in the container.
- As this occurs HCl gas will slowly start to migrate over into the isopropanol container and enter into solution.
- The anhydrous magnesium sulphate serves to remove the remaining 1% of water in the isopropanol as well as any that might come over during the reaction.
Possible improvement that was not attempted:
If you consider that the enthalpy change of protonation is -ve (in other words exothermic) you can shift the reaction equilibrium towards product formation via Le Chatelier's principle.
This can be done by removing heat from the system. Placing the jar in the fridge might help increase the solubility of HCl in the isopropanol although I can't say for certain what will happen.
The original gassing method was also conducted using cold conditions, this is why I mention it.
Proof that this actually works:
A small amount of sodium bicarbonate (baking soda) was placed into a beaker followed by the isopropanol that was now acidic,
after which carbon dioxide was released indicating the presence of dissolved hydrogen chloride.
I didn't fake this, the bicarbonate clearly doesn't dissolve like it would in water.
The effervescence is also extremely slow because the reaction is heterogeneous and not homogeneous like it would be with water present.
Thank you for reading and I hope you found this informative. Cheers!
